1. Field of the Invention
The present invention relates to a sample supplying device for a dry particle-size distribution measuring apparatus, and more particularly, to an improved sample supplying device and method of providing a preliminary dispersion of particles into a primary state during the initial introduction of the sample into the measuring apparatus.
2. Description of Related Art
In a dry particle-size distribution measuring apparatus, usually, a powdery and particulate sample is accommodated in a trough of a sample supplying device which is disposed above a measurement flow cell, and, when the particle-size distribution of the sample is to be measured, the trough may be vibrated by a linear feeder to drop the sample through a drop hole formed in the trough, thereby causing the sample to be supplied into a conduit connected to the flow cell.
However, relatively small particles in a sample, such as powdery and particulate members are sometimes aggregated by an electrostatic force, a Van der Waals force, a magnetic force, or the like which acts among the powdery and particulate members even in a dry state, so that the powdery and particulate members are not formed as so-called primary particles in which powdery and particulate members are completely separated from each other, but rather may be formed as secondary particles (in each of which several primary particles are aggregated) or tertiary particles (in each of which several secondary particles are aggregated). When such powdery and particulate members including not only primary particles but also secondary and tertiary particles are supplied to a flow cell as a sample and measurement is then conducted while irradiating the sample with light, it is difficult to obtain a true particle-size distribution of the powdery and particulate members.
In conventional sample supplying devices, therefore, there has been attempts to employ the following techniques: (1) a sieve member is disposed under the drop hole with a size to prevent such secondary and tertiary particles from being dropped and thereby allow only powdery and particulate members of a predetermined size or smaller relative to the sieve size to be passed; and (2) a plurality of bearing balls are placed in the sieve member, and secondary and tertiary particles are dispersed by rotation and sliding contact with the bearing balls to change them into primary particles.
In both of the above techniques, however, it is difficult to attain a complete state in which a powdery and particulate sample is configured only by primary particles and does not contain secondary and tertiary particles, and additionally the sieve can sometimes be clogged by secondary and tertiary particles, so that powdery and particulate members cannot be smoothly dropped in a predetermined quantity. Particularly, in the case where a sample of a high density is supplied by vibration of a linear feeder, and so-called submicron powdery and particulate members in which the particle size is smaller than 1 μm are charged as a sample, there arises a disadvantage that only dispersion up to 1 μm which corresponds to the secondary particle state may be performed.
Thus, there remains a need in this field of particle measurement to provide a compact and economical solution to these problems.